Leaf' Gilding, on paper or vellum.—This is extremely simple, as the surface requires no other preparation than a wash of dilute gum water, or isinglass size. Upon this the leaves of gold are laid, when it is in a certain state of dryness, which must be known by practice : if it has be come only a little too dry, it may be sufficiently damped by breathing on it. When the surface is covered with gold, it can be burnished with an agate, or dog's tooth.
Gilt Letter.9.—lf it be required to gild manuscript writ ing, a strong size must be used for writing, instead of ink : it is made of gum ammoniac dissolved in water previously impregnated with a little gum arahic, and some juice of garlick ; this forms a fluid of a milky colour, which will flow very readily from a pen, or it can be laid on accord ing to any design by a camel-hair pencil : it may be suf fered to dry, and then, by breathing upon the paper, the size will be softened sufficiently to receive the gold, which is applied in leaves in the same manner as for any other kind of gilding. The superfluous gold being removed by a brush, the writing is found covered, in its finest strokes, with gold which may be burnished. Gold letters for shop fronts, Etc. are painted in oil size, by the process of gilding in oil.
Printing in gold may be performed by beating up the white of eggs to a proper consistence, to mix with vermil lion, and make a thick ink ; with this the paper or vellum must be printed, and the gold applied in leaves, as before directed.
A different method is sometimes employed to ornament paper with gilt letters. This is to use printing ink, com posed of strong gum water ; and the letters, after being printed with this, are sprinkled over with very fine powder of crystal or glass, so as to form when dry, a kind of sand or glass paper upon the form of letters. To gild these parts, it is only requisite to rub them over with a piece of solid gold, and the sharp angles of the crystal will cut of sufficient gold to gild Om writing, which will be very bril liant from the reflections of the crystal. It has been re commended to employ stamps for the printing, in which the letter shall be engraved or sunk, instead of being raised,, as in printing types. The stink parts of these letters are to be filled up with an ink composed of gum, or whites of eggs, and the raised surface being .kept clean, the stamps, when applied upon the paper and pressed, will leave the mixture upon the paper in the form of the letters engraved upon the face of the stamp, and considerably raised. The gilding is performed when the mixture is dry, by rub bing it with apiece of gold as before directed.
Book-hinders imprint gold letters on the backs of books, without any size, by means of brass types, which are cut the same as printing types ; these are made hot in a char coal fire, and are pressed upon the place where the letters are to be, over which a leaf of gold has been previously spread. The heat and pressure causes the gold to adhere to the leather, where the type was applied, but the gold brushes off from the other parts. Set olls and all kinds of ornaments arc impressed in the same manlier ; hut when a length of bordering is required, the impression is engraved on the surface of a small roller, which is used hot, in the same manner as the types.
In order to gild the edges of the leaves of hooks, or writing paper, they must be strongly screwed in a press, alter being cut as smooth as possible, and the edges sized with isinglass glue, mixed up with spirits of wine. The gold should be laid on when the size arrives at a proper de gree of dryness.
The French workmen employ a ground of bole ammo niac, mixed up with powdered snga•candy, by means of white of eggs. This is laid very thinly upon the edges, after isinglass size or gum has been applied. When the ground is dry, it is rubbed smooth with a wet rag, and this moistens it sufficiently to take the gold.
Japanners' Gilding.—Gilding with gold powder is only used where the appearance of frosted gold is desired. The powder is sprinkled upon the article after the cement has been laid on. This method is not so durable as leaf-gild ing, that is, it requires a greater proportion of gold to form an equally effectual covering by this means ; for this reason it is generally covered with a coat of varnish, and is hence called japanners' To reduce the gold to powder, two different means may be employed; one by precipitation, and the other by grind ing. For the first, any quantity of pure gold is put into a glass containing about eight times its weight of aqua regia, (nitro-inuriatie acid.) The gold will more readily dissolve, if it is either beat out into thin plates, or divided into small grains, by pouring it into water when melted. A gen tle heat being applied, will facilitate the progress, and by occasionally stirring it with a glass rod, the gold will be wholly taken up. A solution of sulphate of iron or green vitriol, in about eight times its weight of water, is made at the same time, and if it leaves any sediment, it must be se parated and rendered clear.